1. Field of the Invention
The present invention relates to a belt for a continuously variable transmission. The belt is formed by supporting a large number of metal elements on a pair of right and left metal ring assemblies wherein multiple sheets of endless metal rings are layered. While the belt is wrapped around a pulley and transmits driving force, the contact part between the pulley contact surfaces of the metal elements and the V-face of the pulley is lubricated by lubricating oil supplied from the rotary shaft of the pulley.
2. Description of the Prior Art
Metal elements which are used in metal belts for continuously variable transmissions are described in Japanese Utility Model Registration Application Laid-open No. 62-131143. FIG. 5 shows the above-mentioned conventional metal element 32 comprising an element main body 34, a neck part 36 and an ear part 37 having pulley contact surfaces 39, 39 which are in contact with V-faces 38, 38 of a pulley at both the right and left ends of the element main body 34. When saddle surfaces 44, 44 with which the inner circumferential surfaces of metal ring assemblies 31, 31 are in contact are taken as a reference, the distance h1xe2x80x2 from the saddle surfaces 44, 44 to the inner end in the radial direction of the pulley contact surfaces 39, 39 is set to be larger than the distance h2 from the saddle surfaces 44, 44 up to the inner end in the radial direction of a lateral middle part of the element main body 34. That is to say, at the inner end in the radial direction of the element main body 34, the opposite ends in the lateral direction protrude inwards in the radial direction from the lateral middle part by a distance dxe2x80x2.
When a metal belt is wrapped around the pulley, in order to lubricate the contact part between the V-faces of the pulley and the pulley contact surfaces formed at the opposite ends in the lateral direction of the metal elements, lubricating oil is supplied towards the inner circumferential surface of the metal belt via the rotary shaft of the pulley. At this time, since the opposite ends in the lateral direction of the conventional metal element 32 shown in FIG. 5 protrude inwards in the radial direction, the lubricating oil supplied via the rotary shaft of the pulley is pushed back by the inward protrusions at the both ends of the metal element 32 as shown by the arrows a and it is therefore difficult for the lubricating oil to flow into the contact parts between the pulley contact surfaces 39, 39 of the metal element 32 and the V-faces 38, 38 of the pulley. Furthermore, with regard to the chord sections of the metal belt which extend linearly between the drive pulley and the driven pulley, since it is difficult for the lubricating oil to be discharged from the indentation at the inner end in the radial direction of the metal element 32 (the hatched area in FIG. 5), there is a problem that a contaminant such as a metal powder present in the lubricating oil, will adhere to the metal element 32.
The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to effectively lubricate the pulley contact surfaces of the metal element with lubricating oil supplied via the rotary shaft of the pulley and, moreover, to prevent a contaminant present in the lubricating oil, from adhering to the metal element.
In order to achieve the above-mentioned object, the invention is directed to a belt for a continuously variable transmission which is formed by supporting a large number of metal elements on a pair of right and left metal ring assemblies. The belt comprises multiple layered sheets of endless metal rings wrapped around a pulley for transmitting a driving force. The contact part between the pulley contact surfaces of the metal elements and the V-face of the pulley is lubricated by lubricating oil supplied from the rotary shaft of the pulley. The inner end in the radial direction of a lateral middle part of the metal element, protrudes inwards in the radial direction from the level of an inner end in the radial direction of the pulley contact surfaces formed at opposite ends of the metal elements.
In accordance with the above-mentioned arrangement, when lubricating oil is supplied from the rotary shaft of the pulley to the inner circumferential surface of the belt which is wrapped around the pulley, since the inner end in the radial direction of the lateral middle part of the metal element protrudes inwards in the radial direction from the inner end of the pulley contact surfaces formed at the opposite ends of the metal element, the lubricating oil flows from the lateral middle part to the opposite ends at the inner end in the radial direction of the metal element, thus effectively lubricating the pulley contact surfaces of the metal element. Furthermore, since no cavity is formed at the inner end in the radial direction of the metal element, when the belt is in a chord section between the pulleys, it becomes hard for the lubricating oil to remain at the inner end in the radial direction of the metal element thus preventing a contaminant such as a metal powder from adhering thereto.
In addition, a belt for a continuously variable transmission is characterised in that, with regard to the metal elements, the height to the inner end in the radial direction of the opposite ends in the right-and-left direction relative to the saddle surface supporting an inner circumferential surface of the metal ring assembly, is set to be smaller than the height to the inner end in the radial direction of the lateral middle part relative to said saddle surface.
In accordance with this arrangement, when the height to the inner end in the radial direction of the middle part of the metal element, relative to the saddle surfaces thereof, is set to be at a minimum in the range in which the metal element can survive the compressive load in the right-and-left direction applied from the V-groove of the pulley, the height to the inner end in the radial direction of the pulley contact surfaces relative to the saddle surfaces thereof is set so as to be smaller than the above-mentioned height and the gear ratio range can, therefore, be enlarged by making the metal element approach the rotary shaft of the pulley as closely as possible without restrictions on the position of the inner end in the radial direction of the pulley contact surfaces.
The driven pulley 11 in the embodiment corresponds to the pulley of the present invention and the driven shaft 10 in the embodiment corresponds to the rotary shaft of the present invention.